The present invention relates to a method of producing a plate material having a uniform width and a thickness which varies along the length thereof, as well as to an apparatus suitable for carrying out the method.
The plate material having a uniform width and a thickness gradually varying along the length thereof can be used quite reasonably as a structural member which is subjected to bending moment gradually varying in the longitudinal direction of the material. The use of such a plate material offers various advantages such as the reduction of weight, save of material, simplification of construction and so forth. It is considered, therefore, that there will be an enormous demand for such plate materials, if such materials are commercially available comparatively easily.
This kind of plate material will provide remarkable advantages, particularly when it is used as the material of a leaf spring of a suspension of automobile, such as reduction of weight, save of material, simplification of construction, smoothening of the shock-absorbing characteristic and so on. However, there has been proposed heretofore no method nor apparatus for massproducing such plate materials economically.
Needless to say, there has been proposed to produce a plate material having a thickness which varies along the length of the material, by controlling the roll gap between rolls by which the plate is rolled, as shown, for example, in Japanese Patent Laid-open Publication No. 16660/1974 published on Feb. 14, 1974 and the specification of U.S. Pat. No. 3,820,373 Specification. In these prior arts, however, no consideration is made as to the lateral spreading of the plate material which is caused as a result of the thicknesswise rolling of the material. It is, therefore, necessary to take the final step of trimming in which both the side edges of the rolled material are trimmed to provide a uniform width of the final product. The material removed from the plate member during the trimming is wasted. Thus, the conventional method is not preferred also from the economical point of view.